In many applications, there is a desire to minimize leakage inductances of windings of a transformer. For example, in a switched mode power supply “SMPS” haying the flyback topology, the leakage inductance of the primary winding causes that all the energy charged to the transformer of the flyback power supply via the primary winding cannot be discharged from the transformer via the secondary winding. A known way to reduce the leakage inductances of windings of a transformer is to use interleaved windings where each winding comprises winding portions which are interleaved with corresponding winding portions of one or more other windings of the transformer. An inherent challenge related to interleaved windings is the need to arrange electrical connections between winding portions so as to connect the winding portions to constitute a winding. An electrical connection between two winding portions belonging to a same winding have to form a connection bridge over one or more other winding portions of one or more other windings where the one or more other winding portions are located, in the interleaving arrangement, between the two winding portions of the winding under consideration. The inductance of the above-mentioned electrical connection between the winding portions should be as small as possible in order to avoid weakening or even losing the advantage provided by the interleaved windings, i.e. the reduction of the leakage inductances.
Foil windings are usual in transformers of many varieties and applications because of various advantages of the foil windings. For example, the skin effect does not reduce the effective electrically conductive area so strongly in a flat and thin foil conductor as e.g. in a round wire conductor having a same cross-sectional area. The above-presented challenge related to interleaved windings is present also in a case where foil windings of a transformer are configured to constitute interleaved windings, i.e. there is the need to arrange electrical connections between winding portions of each foil winding so that the inductances of the electrical connections are as small as possible.